The present invention is particularly directed to users who, due to the nature of their situation, are often out of audio range of others. This may be because of distances involved or because of high audio frequency ambient noise generated by machinery or other sources. Some potential users of the present invention include refinery operations personnel, forest rangers, plant security personnel, police officers, facility maintenance personnel, etc. A personnel maintenance system of this nature may also be employed by users engaged in recreational activities such as hiking, hunting, or other circumstances where users may be out of contact with others for extended periods in remote conditions.
Personnel monitoring techniques are presently in use which make use of radio technology for basic safety purposes as a natural extension of the fundamental productivity purposes which the radio systems are installed to achieve. Some simple technology add-ons to basic portable radios are in common use to enhance basic safety capabilities of the radios. For instance, in cases of minor injury, the victim can call for assistance utilizing small radio transceivers or a panic button on the radio may be pushed to send out an emergency alarm signal.
The key problem is that, in cases of serious injury, when the user is immobilized and unable to initiate calls for help, the need for timely rescue is usually greatest. The lack of timely rescue can act to complicate the injury through increased loss of blood or shock or many other time related medical problems. Basic first aid principles are very clear in identifying the critical role time can play in serious injury situations and how minutes or even seconds saved in rescue time can mean the difference between the life or death of the victim.
A number of radio users who recognize this problem have developed timed reporting procedures to keep track of the safe status of personnel. This approach, which relies on users calling in their safe status, has a very serious weakness in its conflict between safety, user productivity, and monitoring logistics. In most situations it is not practical and perhaps impossible for a person to be reporting safe status and efficiently completing the assigned task. Moreover, even in cases of known high risk situations, it is often not practical to monitor the condition of workers at all times. Further, radio channels are limited and in many situations, the radio channels must be shared with others. As a result, most safe status reporting systems work on a reporting-in frequency ranging from every 10-20 minutes or longer. Obviously, there is a need to provide an efficient personnel monitoring and man-down alert system that is capable of immediately and reliably detecting a condition where a worker becomes incapacitated so that the worker may be located and attended to without delay. A less direct benefit of the present invention is the increased safety factor it provides to rescue personnel. When rescue personnel know that time is against them, they tend to rush their response, sometimes to the detriment of their own safety. The fast alarm reporting capability of the present invention can ease time pressure on rescue personnel and thereby increase their own safety without detriment to the personnel for whom the emergency is intended.
User motion is the key to reliable detection of unsafe user status. The lack of motion for a given period of time can be translated into a reliable means to detect an incapacitated person. From the standpoint of detection of motion, the critical factor is the need to be able to differentiate between motion and lack of motion. For example, under circumstances where a user of a motion detector system becomes incapacitated in the vicinity of large machinery, it is necessary that vibrations from the machinery are not misinterpreted as user motion. As a general rule, potential sources of interference will display a detectable pattern while user motion will tend to be random in nature. As such, filtering of interfering detectable input signals can be accomplished.
Another key consideration is that the motion detector must be capable of detecting motion and sensing the lack of motion in all physical planes. An incapacitated person, whether lying, sitting or standing must be capable of detection by absence of motion in that particular position. From the standpoint of reliable detection of incapacitated personnel, it must not be assumed that these personnel will end up flat out on the ground in a horizontal position. In accident situations involving electrical shock, toxic gasses, falls down stairs and numerous other situations, the victim may end up unconscious and/or immobilized in virtually any physical position including upside-down or even standing straight up wedged between pieces of machinery. Reliable detection of incapacitated personnel cannot be related to physical position of personnel. Further, the motion sensing system must render false alarms to an absolute minimum since false alarm signals reduce system integrity and place rescue personnel at unnecessary risk. Even further, the motion sensing system must insure that all lack of motion conditions of personnel be capable of rapid detection so that appropriate aid may be provided without delay in all conditions of personnel incapacitation.